Fragile X syndrome is a sex-linked disorder found mostly in boys, characterized by mental impairment, large ears, a long face, heart defects, and flat feet. It is caused by a mutation to the gene shown in the picture above. The codon CGG is abnormally repeated many times, causing the cell to inactivate the gene. Such a mutation is known as a(n)
A)	insertion.	
B)	inversion.	
C)	deletion.	
D)	duplication.
                                             
                                          
                                          
                                       